/Engine/Source/Runtime/Engine/Classes/Engine/World.h
Add multiple streaming levels to the list of streamed levels to consider. If any of these streaming levels are in the array already then they won't be added again.
void AddUniqueStreamingLevels ( [TArrayView](API\Runtime\Core\Containers\TArrayView)< [ULevelStreaming](API\Runtime\Engine\Engine\ULevelStreaming) *const > StreamingLevelsToAdd )